1. Field of the Invention
The present invention relates to a method of a start-stop control for an internal combustion engine in a vehicle for briefly stopping the internal combustion engine and starting the internal combustion engine, in particular by using an electric machine as a starter, the internal combustion engine being switched off by an engine control when switch-off conditions obtain and the start-stop control querying whether a start signal exists on the basis of switch-on conditions. The present invention also relates to a computer program product as well as a start-stop control for an internal combustion engine in a vehicle.
2. Description of the Related Art
In order to save fuel and emissions, it is known for an engine control to switch off the internal combustion engine in a vehicle according to particular switch-off conditions, in particular following a specific time lapse, for example at traffic lights or at other traffic impediments that necessitate a brief stop. Usually, an internal combustion engine is started by a starter, which has a starter pinion that is engaged into a ring gear of an internal combustion engine. For such constructions of an internal combustion engine, as are started with the aid of a starter pinion, there are minimum time periods for a restart, which must be awaited before the internal combustion engine may be started again.
In addition to classical starters having a starter pinion, belt starters, integrated starters, hybrid drives having a switchable clutch between the electric machine and the internal combustion engine are also known. In the latter constructions, the engagement location for the starter on the internal combustion engine thus varies such that the internal combustion engine is started via a starter pinion, a crankshaft, or via the drive train.
Published German patent application document DE 10 2006 011 644 A1 describes a device and a method for operating a device having a starter pinion and a ring gear of an internal combustion engine, the rotational speed of the ring gear and of the starter pinion being ascertained in order, following the shutdown of the internal combustion engine, to engage the starter pinion at the essentially identical rotational speed as the internal combustion engine is running down. The starter pinion remains in an engaged state until the internal combustion engine is started.
Published German patent application document DE 10 2006 039 112 A1 describes a method for determining the rotational speed of the starter for an internal combustion engine of a motor vehicle. Furthermore, there is the description that the starter comprises a starter control unit of its own to calculate the rotational speed of the starter in order to accelerate the pinion of the starter in a start-stop operation if a self-start of the internal combustion engine is no longer possible due to the reduced rotational speed. The pinion is engaged at a synchronous rotational speed into the ring gear of the internal combustion engine as the latter is running down.
Published German patent application document DE 10 2005 004 326 describes a starting device for an internal combustion engine having a separate engaging and starting process. For this purpose, the starting device has a control unit, which separately controls a starter motor and an actuator for engaging a starter pinion. The control unit is able to engage the pinion into the ring gear prior to a starting process of the vehicle, before the driver has issued a new starting request. For this purpose, the actuator is triggered as an engaging relay already during a run-down phase of the internal combustion engine. The rotational speed threshold here is far below the idling speed of the engine so as to minimize the wear of the engaging device. In order to avoid voltage drops by a very high starting current of the starter motor, the control provides a gentle start, for example by clocking the starter current. The performance of the vehicle electrical system is monitored by analyzing the state of the battery, and the starter motor is clocked or supplied with current accordingly. Furthermore, the invention describes that the crankshaft may be positioned when the internal combustion engine is at a standstill so as to shorten the starting time.
Published German patent application document DE 10 2005 021 227 A1 describes a starting device for an internal combustion engine in motor vehicles having a control unit, a starter relay, a starter pinion, and a starter motor. For a start-stop operating strategy, the armature of the start relay may be advanced at reduced force by a controlled energization in order to engage the starter pinion into a ring gear of the internal combustion engine in a first stage, while in a second stage a switching contact is closed with the full force of the armature in order to supply maximum energy to the starter motor. The starter motor is started via a transistor in the control unit using a controlled current when engaging the starter pinion so that, in the event of a tooth-upon-tooth position, the starter pinion is wound gently into the next tooth gap in the ring gear.